Cutter

ABSTRACT

A cutter suitable for cutting, for example, swaged-on metal collars of lockbolts to facilitate removal of the lockbolts has two blades movable to bring their cutting edges together to cut a collar beteen them, and has resilient guides attached to the blades for guiding the blades to cut a collar or other workpiece symmetrically.

United States Patent 11 1 Savage et al.

[ 51 Sept. 11, 1973 1 CUTTER [75] Inventors: Donald Stanley/Savage,stAlbans;

Paul Edward Presser, Londombotli of England [73] Assignee: Aerpat A.G.,Zug, Switzerland 683,457 10/1901 Flowers 30/131 1,653,340 12/1927Carolus 30/179 FOREIGN PATENTS OR APPLICATIONS 111,821 8/1964Czechoslovakia 30/124 1,033,749 7/1958 Germany 30/187 PrimaryExaminer-James L. Jones, Jr. Attorney-Kemon, Palmer & Estabrook [57]ABSTRACT A cutter suitable for cutting, for example, swaged-on metalcollars of lockbolts to facilitate removal of the lockbolts has twoblades movable to bring their cutting edges together to cut a collarbeteen them, and has resilient guides attached to the blades for guidingthe blades to cut a collar or other workpiece symmetrically.

1 Claim, 9 Drawing Figures PATENTEDSEN mm 3757, 417

SHEET 1 "IF t orney CUTTER This invention relates to a cutter and moreparticularly to a cutter which facilitates the cutting of a workpiece ata desired position.

A particular operation which, it is thought, the invention mayfacilitate is the removal from an assembly of a fastener of the kindknown as a lockbolt which is secured in position by an annular collarswaged on to the stern of the lockbolt. The cutter may be used to cutthe collar substantially diametrically into two parts so that the partsfall away from the stem, leaving the stem free to be withdrawn from theassembly.

The collar of a lockbolt is usually of substantially cylindrical shapeand is circular in cross section: and the stem of the lockbolt extendsaxially through the bore of the collar. The most expedient way ofremoving the collar is to cut it longitudinally from diametricallyopposite positions on its periphery. This, however, is difficult toachieve with conventional tools: for example, conventional bolt-croppersare difficult to position so as to cut the collar diametrically and havea tendency to slip away from this position.

According to the present invention, there is provideda cutter comprisingtwo opposed blades relatively movable towards each other to cut aworkpiece between them, and a guide associated with each blade, the twoguides being disposed on mutually opposite sides of the pair of bladesand being arranged so that, when the blades are moved towards each otheras aforesaid, the guides engage respectively with mutually opposedpositions on the workpiece between the blades, thereby to assist inpositioning the cutter blades in the appropriate positions with respectto the workpiece to facilitate cutting thereof.

When a symmetrical workpiece is to be cut symmetrically the shape anddisposition of at least thoseparts of the guides which engage theworkpiece are symmetrically arranged withrespect to the cutting plane ofthe cutter. The aforesaid part of each guide member. may be inclined tothe direction in which the cutter blades are relatively movable towardseach other,- and may also be inclined to a direction parallel to theaforesaid axis of symmetry when the cutter is in use.

The guides may be resilient or resiliently mounted, and each may bemounted on its associated blade for movement therewith. In apreferred-embodiment of the invention, the guides are themselvesresilient and are made of spring steel strip. Also in a preferredembodiment of the invention, each guide is secured to one side of itsassociated blade and has a workpiece engaging part which is disposed onthe other side of the associated blade, the guide extending around theback (i.e., the part remote from the other blade) of the associatedblade.

A specific embodiment of the invention will now be described by way ofexample and with reference to the accompanying drawings, in which: I

FIG. 1 is an elevation of a cutter;

FIG. 2 is another elevation of the cutter, taken at right-angles to thatof FIG. 1;

FIG. 3 is a partly sectional elevation, otherwise similar to FIG. 1;

FIG. 4 is an elevation of one of the cutter blades and its associatedguide member;

FIG. 5 is a section on the line V-V of FIG. 4;

FIG. 6 is a section through a particular form of workpiece which thecutter is adapted to cut;

FIG. 7 is similar to FIG. 6 but shows the cutter (similarly to FIG. 3)applied to the workpiece before cutting commences;

FIG. 8 is a section on the line VIII-VIII of FIG. 7; and

FIG. 9 is similar to FIG. 8 but shows the position when the cutting isnearly completed.

The cutter of this example is designed and adapted to perform a cuttingoperation on a swaged collar of a lock-bolt. Referring first to FIG. 6,there is shown a well known form of lockbolt securing together twoapertured metal sheets 11, 12. The lockbolt comprises a stem 13 whichextends through aligned apertures of the two sheets, and a collar 17.The stem has an enlarged head 14 on one end and a swaging portion 15comprising alternate circumferential grooves 15 and lands 16 at theother end. The collar 17 has been swaged into the grooves by means of apowerful hydraulically operated swaging tool so that the collar issecured to the stem. The stem is under considerable tension and the twosheets are clamped together between the head of the stem and the collar.Such lockbolts are sold in many countries of the world under thetrademarks Huckbolt and Avdelok.

Such a lockbolt, once placed, is normally considered to be a permanentfixture, but it is sometimes necessary to undo and'remove the fastening.The cutter of the present example is adapted to facilitate cutting orsplitting of the swaged collar of the lockbolt, and comprises twoopposed blades 21, 22 both mounted between two rigidly interconnectedopposed cheek plates 23, 24. The blades are pivotally mounted atapproximately their middle positions on pivot pins 25,-26 respectively,and have tail portions l8, 1.9 which extend rearwardly of the pivot pinsand between the cheek plates and cutting portions which extend forwardlyof the pivot pins and'beyond the cheek plates and which are bevelled toprovide straight cutting edges 27, 28 respectively opposed to eachother. The blades are urged to pivot towards the open position (i.e.,with their cutting edges 27, 28 apart from each other) by means of twosprings 29, 31 respectively, mounted between the ckeek plates, whichurge the tail parts 18, 19 towards each other.

. The adjacent surfaces 33, 34 of the tail parts l8, 19 of the bladesare inclined towards each other in the rearward direction away from thepivot pins. A cam 32 which lies between the surfaces 33, 34 .and bearsagainst them is secured to or integral with one end of a drawbar 35,which has at its other end an internal threaded connection socket 36.The blades can be moved towards the closed position (i.e., moving theircutting edges 27, 28 towards each other) by rearward movement of the cam32. The drawbar 35 extends rearwardly through a tube 37 which is securedat its forward end to the cheek plates 23, 24. The tube is provided withcoupling lugs 38 near its other end. The tube 37 and drawbar 35 areadapted to be connected, by means of the lugs 38 and threaded socket 36respectively, to the head of the hydraulic pulling tool of the typewhich is normally used for the swaging of lockbolts which the cutter isintended to be used on. When the cutter is connected to the hydraulicpulling tool and the tool is operated, the drawbar 35 is pulled withconsiderable force through a suitable stroke rearwardly with respect tothe tube 37. As the cam 32 moves rearwardly along the inclined surfaces33, 34 of blade tails l8, 19, the tail portions of the blades are forcedapart causing the blades to pivot, thus causing their cutting edges 27,28 to move towards each other with a force sufficient to cut through theswaged collar 17 of the lockbolt.

It will be apparent from FIGS. 6, 7, and 8 that the shape of theexterior surface of the swaged collar 17 is of generally symmetricalabout the axis of the lockbolt pin, and that it tapers towards its freeend, and is slightly of concave or saddleback curvature in thelongitudinal direction.

The cutter of this example has secured to its blades guides 41, 41awhich assist in positioning and retaining the cutter blades indiametrically opposed positions on the periphery of the collar 17,whilst the blades cut the collar.

The two blades 21, 22 are identical, and each blade and its associatedguide together is identical with the other blade and its associatedguide. (Since the two guides are identical, the parts of the guide 41aassociated with the cutter blade 22 are designated in the drawings bysimilar reference numerals to those of the guide 41 associated withcutter blade 21 but with the addition of the suffix a.) The blade 21 andits associated guide 41 are illustrated in FIG. 4 and 5. The guide 41 ismade of spring steel strip and, as-illustrated in FIG. 5, is generallyof U-shaped section, having a short arm 42 and a long arm 45 joined byan arcuate web 44. Each guide extends along the. cutting portion of itsassociated blade over a zone which is rather shorter than the length ofthe cutting edge and which stops short of each end of the cutting edge.The arm 42 of the guide is secured in contact with one side face of theblade 21 by means of two rivets 40 passing through the blade and thearm. The free end part 43 of the arm 42 is bent inwardly of the U so asto lie in contact with the cutting bevel of the blade. The arcuate web44 of the guide extends around the back of the blade (i.e.,

the part remote from its cutting edge 27) and is spaced away therefrom.The long arm 45 of the U-shaped guide 41 has a flat portion adjacent tothe web 44 which portion extends parallel to the other side face of theblade 21 but slightly spaced away therefrom. The arm 45 is provided withtwo circular holes 46 .(in FIG. 3 the two corresponding holes 46a on theother guide 41a are indicated) which allow the rivets 40 to be set whensecuring the guide to the blade. The long arm 45 extends beyond thecutting edgeof the blade with a connecting portion 47 which is inclinedinwardly of the U and ends in a flat, outwardly inclined,workpieceengaging portion 48.

It will be seen from FIGS. and 8 that the workpiece engaging portions48, 48a of the two guides are inclined to a line extending between thecutting edges of the two blades and are also inclined to a line parallelto the two cutting edges 27, 28. The arrangement is such that, in use ofthe cutter, each of the workpiece engaging portions 48, 48a issubstantially tangential to the part of the surface of the lockboltcollar which it engages.

The manner of use of the cutter is illustrated in the FIGS. 7, 8 and 9.With the cutter blades in the open position (as illustrated in FIGS. 1and 3), the cutter is offered up to the collar 17 so that the collarenters between the cutting edges 27, 28 and also between the twoworkpiece-engaging portions 48, 48a of the guides.

The portions 48, 48a of the two guides engage the collar atdiametrically opposed positions on the collar. Since the collar issymmetrical, and the two guides are identical and therefore havesubstantially the same deflection rate, the two guides guide the cutterso that the collar becomes centered between the cutting edges 27, 28.The cutter is pushed fully onto the collar so that the two cutting edges27, 28 extend along the entire length of the collar, as illustrated inFIG. 7. In this example, since the shape and the dimensions of theblades and guides is designed to suit the particular dimensions of thelockbolt collar on which they are being used, the two guides are incontact with the lockbolt collar but are substantially undeflected inthis position. Since the guides do not extend quite as far forwardly asthe forward ends of the blades, the guides do not engage the sheet 12and so do not mark or scratch it.

The hydraulic tool to which the cutter is connected is now operated,thus progressively closing the cutting edges of the blades together withconsiderable force. It is found in practice that this initially causesthe swaged collar to collapse between the cutting edges of the bladesand to expand in the direction at right angles as shown somewhatschematically in FIG. 9, thus forcing the guides apart. It will be seenthat, since the arrangement is symmetrical, the arms 45, of the twoguides are both deflected by a similar amount and it is found that themajority of the deflection is accommodated in the region of the arcuateweb 44 of each guide and in particular at the junction between the web44 and the adjacent flat portion of the arm 42 which is secured to theblade. The deflection of the guides will apply to each blade of thecutter a twisting force or torque about its longitudinal axis, but theconstruction of the cheek plates and pivot pins of the cutter issufficiently strong to resist this torque and prevent any substantialmisalignment of the cutting edges of the blades.

As the cutting edges of the blades are urged closer together, theyeventually penetrate through the thickness of the collar which isthereby cut into two halves which separate and release the stern of thelockbolt. Due to the force with which the cutter blades penetrate thecollar, the two halves of the collar tend to fly apart with some forcewhen finally separated. The guides absorb the kinetic energy of thecollar halves and protect the operator from the danger of being struckby flying parts of the split collar. In practice it is of course foundthat the swaging portion of the lockbolt stem is also damaged by thecutter blades, but this is of no importance since in any case the stemcannot be re-used with a new collar.

The cutter of the foregoing example is advantageous in that it providesa simple and accurate means of guiding the cutting edges to suitablecutting positions on the lockbolt collar and of maintaining them sopositioned until the cutting process is complete. Without such guidingmeans, it is found to be very difficult to hold the cutter so that thecutting edges cut or bite into the collar at diametrically oppositepositions with the result that the blades tend to slide off the collar.In particular, providing a guide associated with each cutting blade, sothat the two guides are on respectively opposite sides of the pair ofblades, allows each guide to be extended around the back of the bladethus providing a considerable length of spring material in which thedeflection of the workpiece engaging portions of the guide arms can betaken up during the cutting process. This reduces stress in the guideand increases the life of the guide.

The invention is not restricted to the details of the foregoingexamples. For instance, the cutter could be of the type of which the twoblades are not pivoted but move towards each other without pivotalmovement. In particular, the cutting edges could be parallel to eachother in both the open and closed positions of the blades. The cuttercan also be used for cutting other things than swaged collars oflockbolts. The precise configuration and construction of the guidesneed-not be exactly as shown in the accompanying drawings. They could bedesigned to engage and co-operate with workpieces which are of differentshapes. The guide members need not be resilient in themselves but couldinstead be rigid members each resiliently mounted upon the cutter blade.Other arrangements than a powered pulling tool for producing therequired cutting movement of the blades can be employed. The cuttercould be operated manually, by being attached to a suitable manual toolinstead of by a power tool.

We claim:

1. A cutter comprising two opposed blades and two guides, the bladesbeing relatively movable towards each other to cut a workpiece betweenthem, each guide being of U-shape and formed of spring steel, each guidecomprising two arms joined by a web, one of said arms constitutingworkpiece-engaging means and the other of said arms constitutingblade-engaging means, each blade having one of the guides associatedtherewith, wherein the blade-engaging means of each guide is disposed incontact with one side of its associated blade and the web of the guideextends freely round the back of the associated blade and theworkpieceengaging means is disposed on the other side of the associatedblade and extends forwardly of the cutting edge thereof, theworkpiece-engaging means of the two guides being disposed on mutuallyopposite sides of the two blades, only the blade-engaging means of eachguide being secured to its associated blade so that theworkpiece-engaging means of each guide is freely movable resilientlyaway from the workpiece-engaging means of the other guide.

* l i l

1. A cutter comprising two opposed blades and two guides, the bladesbeing relatively movabLe towards each other to cut a workpiece betweenthem, each guide being of U-shape and formed of spring steel, each guidecomprising two arms joined by a web, one of said arms constitutingworkpiece-engaging means and the other of said arms constitutingblade-engaging means, each blade having one of the guides associatedtherewith, wherein the bladeengaging means of each guide is disposed incontact with one side of its associated blade and the web of the guideextends freely round the back of the associated blade and theworkpiece-engaging means is disposed on the other side of the associatedblade and extends forwardly of the cutting edge thereof, theworkpieceengaging means of the two guides being disposed on mutuallyopposite sides of the two blades, only the blade-engaging means of eachguide being secured to its associated blade so that theworkpiece-engaging means of each guide is freely movable resilientlyaway from the workpiece-engaging means of the other guide.